The $5100 is a tort damages payment only, for the reduced value of the car due to VW's fraud.
Clause 4.9.1:
If, by June 15, 2018, there is no Approved Emissions Modification, or second stage of an Approved Emissions Modification, for Eligible Vehicles with a particular Generation of engine, Settlement Class Members who own such Eligible Vehicles will be informed by a Class Update that, if they have not already made a Claim, or if no benefits under the Settlement Agreement have been received in respect of their Eligible Vehicle, they may opt out of the Settlement Class during the Second Opt-Out Period , except that they will receive their applicable Damages Payment.
Yikes. If you are going to quote something you cant just quote the parts you want so that it makes your point. Here is the entire clause 4.9.1 (with the key part you omitted in bold)
Owned Vehicles. If, by June 15, 2018, there is no Approved
Emissions Modification, or second stage of an Approved
Emissions Modification, for Eligible Vehicles with a particular
Generation of engine, Settlement Class Members who own such
Eligible Vehicles will be informed by a Class Update that, if they
have not already made a Claim, or if no benefits under the
Settlement Agreement have been received in respect of their
Eligible Vehicle, they may opt out of the Settlement Class during
the Second Opt-Out Period
or, if they remain in the Settlement
Class, or if their Eligible Vehicle has been modified with the first
stage of an Approved Emissions Modification, they may choose
a Buyback or Buyback With Trade-In regardless of whether they
meet the definition of an Eligible Owner, in which case
Sections 4.2.3 through 4.2.5 and Schedules “B” and “E” will
apply to them as if they are Eligible Owners for purposes thereof,
except that they will receive their applicable Damages Payment,
or fifty percent (50%) of the applicable Damages Payment if their
Eligible Vehicle has been modified with the first stage of an
Approved Emissions Modification. For avoidance of doubt, if a
Class Update is issued on or before June 15, 2018 identifying
that there is an Approved Emissions Modification, or a second
stage of an Approved Emissions Modification, for Eligible
Vehicles, this Section shall not be applicable to owners of such
Eligible Vehicles.
The "except they will receive their applicable damages" phrase applies if you opt for a buy back in the case when there is no modification approved. The buy back will be available to more types of owners, including those that purchased after Sept 2015, who would otherwise not be eligible for a buy back. The "except they will receive their applicable damages" phrase limits their damages payment to what they would have received as an Eligible Purchaser.
Anyways, its a complicated clause, so you need to read it carefully and you can't just skip the parts you don't like.
Bottom line, if there is no mod and you don't do the buy back you don't get the payment.